Sheep Body Lice

Sheep body lice (Bovicola ovis) are biting insects that cause affected animals to become itchy. Signs of lice infestation include rubbing, biting and scratching. Lice are a common problem in Victorian sheep flocks, but most importantly are controllable, eradicable and preventable. Significant economic
losses result from decreased wool quality and quantity, high treatment costs, and limited sale opportunities. Sheep lice usually spread by direct body contact between sheep. Humans may spread lice on their clothing and footwear, but this is a remote possibility compared to the risk of stray, or purchased,
infected sheep.

Biology of the sheep body lice

The sheep body louse (Bovicola ovis) is a cream-coloured insect 1-2 mm long with a red-brown head. It feeds on dead skin, lanolin, sweat gland secretions and skin bacteria.

When mature, the female louse lays approximately 1 egg every day for a month. The cycle from egg to adult-layer only takes 34-36 days, and takes place entirely on the sheep. Short cool days during the winter months are the preferred conditions for sheep lice reproduction although buildup can occur
at other times but at a reduced rate.

Shearing removes 30 to 50% of lice population on a sheep and solar radiation kills most of the remainder on late Spring/ Summer shorn sheep. Hence, untreated, Summer shorn sheep, will go into Autumn with very low lice populations.

The relatively slow rate of reproduction during the warmer time of the year means that it will take months for lice populations to build to a heavy infestation. Lice may be present for some time before rubbing and wool on fences, draws attention to their presence in a sheep flock.

Signs of lice infestation

Lice are only one cause of irritation to sheep, so a detailed inspection of the mob should be undertaken to establish the true cause. As lice are small insects they can be quite difficult to see, however most people can see them with the naked eye in good light, particularly if large numbers are present.

The best way to check for lice is by parting the wool a number of times where sheep are rubbed or matted. Otherwise make at least 10 partings on each side of the sheep, moving down the neck and along the side to the thigh. With the sunlight shining on the skin, lice can be seen moving away from the
parted area back into the wool, as they do not like to be exposed to sunlight.

Protected areas, such as the folds around the neck, are preferred areas for the insects on bare shorn sheep. In woolly sheep, the mid-sides generally have the greatest lice numbers.

Any mobs that you suspect are infected should be thoroughly checked, as should all mobs before shearing.

If on inspection lice are found, eradication and future prevention are necessary.

Further information

Agriculture notes detailing control and eradication programs as well as avoiding introducing sheep lice are available. For further information please contact your local animal health staff at the Department of Primary Industries.

Acknowledgements

This Information Note was originally developed by Louise Wood, Katie Rutter and Richard Keys and was previously published in October 2003.

Published and Authorised by:Department of Environment and Primary Industries1 Spring StreetMelbourne, Victoria

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